Recorded 28 January 2025. Adrian van Kan of the University of California, Berkeley, presents "Simulating Rotating Convection at Very Small But Finite Ekman Numbers" at IPAM's Rotating Turbulence: Interplay and Separability of Bulk and Boundary Dynamics Workshop. Abstract: Geophysical and astrophysical fluid flows are typically driven by buoyancy and strongly constrained at large scales by planetary rotation. Rapidly rotating Rayleigh-Bénard convection (RRRBC) provides a paradigm for experiments and direct numerical simulations (DNS) of such flows, but the accessible parameter space remains restricted to moderately fast rotation rates (Ekman numbers Ek≳10−8), while realistic Ek for astro-/geophysical applications are orders of magnitude smaller. On the other hand, previously derived reduced equations of motion describing the leading-order behaviour in the limit of very rapid rotation (Ek→0) cannot capture finite rotation effects, and the physically most relevant part of parameter space with small but finite Ek has remained elusive. Here, we employ the rescaled incompressible Navier-Stokes equations (RiNSE) -- a reformulation of the Navier-Stokes-Boussinesq equations informed by the scalings valid for Ek→0, recently introduced by Julien et al. 2024 -- to provide full DNS of RRRBC at unprecedented rotation strengths down to Ek=10−15 and below, revealing the disappearance of cyclone-anticyclone asymmetry at previously unattainable Ekman numbers (Ek≈10−9). We also identify an overshoot in the heat transport as Ek is reduced at fixed Ra˜=RaEk4/3 , associated with dissipation due to ageostrophic motions in the boundary layers. The simulations validate theoretical predictions based on thermal boundary layer theory for RRRBC and show that the solutions of RiNSE agree with the reduced equations at very small Ek. These results represent a first foray into the vast, largely unexplored parameter space of very rapidly rotating convection rendered accessible by RiNSE. Learn more online at: https://www.ipam.ucla.edu/programs/workshops/rotating-turbulence-interplay-and-separability-of-bulk-and-boundary-dynamics/